With maturity of the packet switching (PS) technologies, the circuit switching (CS)-based traditional telecom networks is developing toward PS-based broadband telecom networks. Using the Session Initiation Protocol (SIP) as a call control signaling of the PS telecom core network is one of the current technical trends. For example, both the International Telecommunications Union-telecom standards part (ITU-T) and the European Telecom Standard Institute (ETSI) currently use the IMS network architecture defined by the 3rd Generation Project Partnership (3GPP) as a core network of the Next Generation Network (NGN).
In the new PS telecom network, the new PS terminal—SIP terminal gradually replaces the traditional terminal telephone set. In the Telecom and Internet converged Services and Protocols for Advanced Networking (TISPAN) affiliated to the ETSI, the services that are provided to the SIP terminal users in an NGN and have feature same as traditional services are collectively called Public Switched Telephone Network/Integrated Services Digital Network (PSTN/ISDN) simulation services. The TISPAN sets up multiple work items (WIs) to study the simulation services, for example, Originator Identifier Presentation (OIP), and Terminal Identifier Presentation (TIP), and Malicious Call Identification (MCID).
In the TISPAN standards, the service logics of the OIP, TIP, and MCID services are implemented on an Application Server (AS). The MCID service and the OIP service need to identify the calling party identifier of a session, and the TIP service needs to identify the called party identifier of a session. When a user is located in an IMS network, the user identifier is carried in the P-Asserted-Identity header field of the SIP message, and the P-CSCF inserts the P-Asserted-Identity header field that carries the user identifier into the SIP message.
When the user is located in a CS domain network, the user identifier is transferred through the Calling Party Number parameter and the Connected Number parameter in a Signaling System No. 7 (SS7) message. To obtain the user identifier of the CS domain network from the IMS network, the Media Gateway Control Function (MGCF) unit needs to map the Calling Party Number parameter and the Connected Number parameter to the P-Asserted-Identity header field of the SIP message. However, the CS domain network does not require provision of the user identifier. Therefore, when an SS7 message does not carry the Calling Party Number parameter or the Connected Number parameter, the MGCF fails to obtain the user identifier of the CS domain network user, thus making it impossible to implement the subsequent services. To enable the IMS network to obtain the user identifier of the CS domain network user, at the TISPAN#11ter conference, the DT puts forward, in the 11tTD273 draft, a method for obtaining the calling party identifier from the MCID service. FIG. 1 shows the process of implementing an MCID service in the prior art, which includes the following steps:
Step 101: When handling the MCID service, the AS of the IMS network detects that the signaling message from the CS domain network does not carry calling party identifier, and hence requests the calling party identifier from the MGCF through an extended SIP message.
Step 102: Upon receiving the request for the calling party identifier, the MGCF sends an identification request (IDR) message to the CS domain network.
Step 103: Upon receiving the IDR message, the CS domain network returns the calling party identifier to the MGCF through an identification response (IRS).
Step 104: Upon receiving the IRS message, the MGCF sends the calling party identifier carried in the message to the AS. The AS performs MCID service processing according to the calling party identifier.
This method has the following weaknesses: Firstly, the existing SIP protocol needs to be extended, which makes it more difficult to implement; secondly, the AS needs to perform signaling interaction with the MGCF, which makes it more complex to process network interfaces and AS services.